The invention relates to a clamping screw.
Such clamping screws, which are loaded by pulling forces and transverse loads, are used in mounting rails, for example, in anchoring rails in construction technology. They have a screw shaft with a thread and a screw head that is hammer-shaped and received in a positive-locking manner in a T groove of the construction component, for example, a mounting rail having a C profile. The screw head can be inserted into the T groove through a longitudinal slot and is brought into the mounting position by rotation about approximately 90.degree.. In the mounding position the screw head with clamping portions engages under support legs of the T groove positioned at both sides of the longitudinal slot. By tightening a nut onto the screw shaft, the clamping screw is then secured at any desired location in the longitudinal direction of the T groove. The clamping portions are positioned at both free ends of the screw head. Between them, a socket, having a greater height and supporting the shaft, may be provided, which has alignment surfaces which are positioned parallel to a transverse axis of the screw head extending centrally through the screw shaft.
The clamping portions of the screw head in this clamping screw have leading edges and following blocking edges in the rotational direction of tightening. The blocking edges have a greater diametric distance then the leading edges so that for preventing a further rotation of the screw head past the mounting position they can be supported at the groove wall of the T groove. The blocking edges provide an abutment for the tightening moment upon placement of the nut and secure the screw head in the mounting position within the T groove transverse to the longitudinal slot.
The mounting position of the clamping screw for a preset dimensioning of the T groove depends on the geometry of the screw head. The clamping screw, and also the mounting rail, can be produced, because of manufacturing-technological reasons, only with tolerances with regard to the final dimensions. In known clamping screws, the fitting tolerances result in an unsatisfactory alignment of the clamping screw within the mounting rail. When a clamping screw with maximum tolerances of the screw head is clamped at a narrow location of the T groove having smallest tolerances, then the screw head is secured prematurely by abutment of the blocking edges and cannot be brought into the ideal mounting position. In the most unfavorable situation of tolerances, the screw head is positioned at a slant within the T groove so that it does not have the predetermined rotational position relative to the mounting rail and the clamping portions of the screw head are only clamped in an unsatisfactory manner at the legs of the mounting rail. When the dimensions of the screw head are within the lower tolerance range and those of the mounting rail are within the upper tolerance range, it is possible, when tightening that the screw, head is turned too far within the T groove, i.e., past the mounting position.
It is an object of the invention to embody the clamping screw of the aforementioned kind such that it is inserted substantially position-exact and with sufficient clamping force into the construction component, e.g., a mounting rail.